Sand consolidation composition

ABSTRACT

METHOD OF AND COMPOSITION FOR THE TREATMENT OF UNCONSOLIDATED SANDY FORMATIONS TO STABILIZE THE FORMATION COMPRISING INJECTING A TREATING COMPOSITION OF 25-100% BY VOLUME OF ACROLEIN DIMER AND 75-0% BY VOLUME OF AN OXYGENATED HYDROCARBON SOLVENT INTO SAID FORMATION, EFFECTING POLYMERIZATION OF SAID DIMER AND FORMATION OF A FLUID PERMEABLE CONSOLIDATED SAND IN SAID FORMATION.

United States Patent Office 3,634,302 SAND CONSOLIDATION COMPOSITIONBobby G. Harnsherger, Houston, Tex., assignor to Texaco Inc, New York,N.Y. No Drawing. Original application Dec. 23, 1968, Ser. No. 786,430,now Patent No. 3,537,521, dated Nov. 3, 1970. Divided and thisapplication Dec. 31, 1969, Ser.

Int. or. cost 45/34 US. Cl. 260-32.8 R 8 Claims ABSTRACT OF THEDISCLOSURE This application is a divisional application of myapplication Serial No. 786,431, filed Dec. 23, 1968, now US. Pat. No.3,537,521, issued Nov. 3, 1970.

The present invention relates to the treatment of permeable undergroundformations. More particularly, the present invention relates to a methodof treating permeable underground oil and/or gas containing formationsto stabilize the sandy portion thereof and to a treating compositionuseful in the stabilization of incompetent sand containing undergroundformations.

The recovery of fluids such as gas and/or oil from undergroundformations has been troublesome in areas wherein the undergroundformation is composed of one or more incompetent sand containing layersor zones. The sand particles in the incompetent zone and/r layer tend tomove or migrate to the well bore during recovery of the formation fluidsfrom the particular zone and/or layer and frequently the moving sandparticles block the passageways leading to the well bore. Plugging ormaterially impairing the flow of the formation fluids toward the borehole results in a loss of these fluids to the producer or so decreasesthe rate of oil recovery from the well as to cause the Well to be shutdown because it is economically unattractive to continue to producetherefrom. An additional adverse factor resulting from the movement ofthe sand particles toward the well bore is that they are often carriedalong with the formation fluids to the well bore and passed through thepipes, pumps, etc. being used to recover the formation fluids to thesurface with resulting damage to the moving parts thereof as the saidparticles are very abrasive.

Many attempts have been made heretofore to prevent or decrease the flowof undesirable sand particles from the formation and into the productiontubing and associated equipment, such as by the placement of sandscreens, filters, liners and so forth. These prior attempts have beenunsuccessful for a number of reasons among which is that thesemechanical devices fail to prevent completely the flow of the formationparticles into the production equipment. In addition these devicesinterfere with various types of the completion and workover operations.In recent years, the industry has attempted to avoid the difiicultiesencountered in the use of mechanical devices by employing variouschemical compositions to effect consolidation of the undergroundincompetent formations. These methods have generally consisted ofinjecting into the underground formation polymerizable resinousmaterials which when subsequently polymerized form permeable barriers inthe formation to prevent the sand particles from movement therethrough.However,

3,634,302 Patented Jan. 11, 1972 this technique of sand consolidationhas not met with w1despread acceptance because of the inherentdifficulties of effecting polymerization of the resinous materials inthe formation to a degree suflicient to consolidate these undergroundformations and yet permitting the unobstructed flow of the desirableformation fluids therethrough. Further, the cost associated with theseresin coating methods has been relatively high in comparison with theprior mechanical methods, and the time required for resin polymerizationis often long at low temperatures.

By the method of the present invention one is able to treat effectivelythe underground formation to be stabilized in a rapid and efficientmanner while minimizing the disadvantages of these prior art methodsboth mechanical and chemical.

One object of the present invention is to provide an improved method oftreating underground sand containing formations to stabilize theincompetent formation. An additional object is to provide a fluidpermeable consolidated formation sand between the loose formation sandand the well bore to prevent or to minimize the flow of unconsolidatedsand particles therethrough while maximizing the flow of desired fluidsand particularly petroleum hydrocarbons therethrough. A still furtherobject is to provide a novel treating composition for use in stabilizingincompetent sand formations and to a method of placing same.

How these and other objects of the invention are accomplished willbecome apparent with reference to the accompanying disclosure. In atleast one embodiment of the method of this invention at least one of theforegoing objects will be obtained.

It has been discovered that an improved method of treating anincompetent sand containing underground formation comprises introducinginto said formation a treating composition consisting essentially of anacrolein dimer which may be dissolved or dispersed in a suitablesolvent, and polymerizing the acrolein dimer as hereinafter more fullydescribed to consolidate the formation. The resultant consolidated sandserves to prevent or to materially reduce the flow of the unconsolidatedsandy particles therethrough while permitting the flow of desirableformation fluids at a substantially unimpaired rate.

In carrying out the method of the present invention the treatingcomposition of acrolein dimer or acrolein dimer in the solvent is pumpeddown the well bore under suflicient pressure to force the compositioninto the unconsolidated formation. When the composition is placed in theformation to be consolidated the dimer is polymerized by a gaseouscatalytic agent or by a combination of the catalytic agent and heat.There is formed a fluid permeable consolidated sand that prevents ordecreases the movement of the unconsolidated sand particles therethroughinto the well bore. The dimer component of the composition sets up andhardens as polymerization occurs. After the dimer polymerizes andhardens the well can be equipped for production and the formation fluidscan be recovered by passing through the resulting formed consolidationinto the well bore and recovered therefrom without the formation fluidsbeing contaminated with the presence therein of unconsolidated sandparticles.

The method of the present invention is particularly adaptable for use inany type of well completion but is generally used in a well whereincasing has been set and which has perforations therein at the desiredintervals 'behind which the unconsolidated formation sands are located.Packers can be initially set above and below the perforated intervals toprevent the treating composition from passing into the non-isolatedportions of the well and also to permit build-up of sufiicient pressureson the said composition to force same through the perforations and intothe formation without plugging up the well bore. After the treatingcomposition has been forced through the casing perforations and into theformation and after polymerization of the dimer, the well is closed into permit the polymer to set.

The treating composition useful in the method of the present inventionmust meet certain specific requirements. The concentration of acroleindimer present in the treating composition can vary from about 25 to 100%by volume with excellent results being obtained at dimer concentrationsof between 40 and 75% and particularly at about 50% for the mosteffective results. Concentrations below about 25% are not desirablebecause the resulting consolidation is too weak.

The solvent component may be an oxygenated aliphatic hydrocarbon solventor an aromatic hydrocarbon solvent or a petroleum fraction to effectsolubilization of the dimer. Representative oxygenated aliphatichydrocarbon solvents include acetone, methylethylketone, methanol,

ethanol isopropanol, and mixtures of such solvents. The preferredsolvent is acetone since it seems to adsorb traces of water from thesand grains when the treating solution is placed in the formation.Representative aromatic hydrocarbon type solvents include benzene,toluene, xylene and mixtures thereof.

Selected petroleum fractions have been found suitable as the solventcomponent such as a kerosene or diesel fraction having a cetane numberof at least about 45, an IBP of about 310 and an EP of about 530 F. or anaphthalene petroleum fraction from a topped catalytic reformate bottomsout having an API Gravity of about 20, an IBP of about 370 and an EP ofabout 750 F. or mixtures thereof.

One can also employ mixtures of the oxygenated aliphatic hydrocarbons,aromatic hydrocarbon type and the petroleum fraction as the solvent.

The gaseous catalytic agent for the treating composition must be onethat on contact the dimer will effect rapid polymerization of theacrolein dimer. Suitable gaseous catalytic agents include nitrogentetroxide, sulfur dioxide, sulfur trioxide, hydrogen halides such ashydrogen chloride and the like, preferably hydrogen chloride. Thesegaseous catalysts can be employed alone or in an inert gaseous carriermedium such as air or nitrogen, carbon dioxide, and the like. One mayuse gaseous hydrogen chloride catalyst in combination with heat (eitherexternally added or by an inert carrier gas or from the heat of theformation itself or from both sources) when very rapid dimerpolymerization is desired.

When one desires to attain superior compressive strength in theconsolidated sand formation, it is advantageous to employ a silanebonding agent such as gammaglycidoxypropyl-trimethoxysilane in the dimercomposition. This material functions to improve surface adhesion of thedimer to the sand grains so that the resultant polymer also has improvedadhesion to these grains and one achieves improved compressive strengthin the consolidated sand.

This material or other silanes of similar type is used in an amount offrom about 0.01 to 3.0% by volume of the dimer solution, preferablyabout 0.5 to 2.0% by volume.

The composition of the present invention is preferably employed in thefollowing manner.

The formation sand to be consolidated is preferably flushed with apetroleum fraction such as kerosene or diesel oil to remove crude oiland some connate water from the formation. The formation is next flushedwith a water and oil miscible solvent such as acetone, methanol, orisopropyl alcohol to remove remaining traces of oil and all connatewater. This pretreating step will enhance the bonding of the polymerizeddimer to the sand grains of the consolidation.

The composition containing the acrolein dimer desirably in solution inthe solvent is introduced into the bore hole and placed adjacent to theunconsolidated sand particles in the formation. Following introductionof the treating solution into the formation one can displace thetreating solution further into the sand consolidation area by employingan inert flushing gas such as nitrogen. The flushing gas also serves toopen the formation pores by removing some of the treating solutiontherefrom.

The treated formation then is contacted with the gaseous catalyticmaterial, preferably hydrogen chloride in nitrogen, to polymerize theacrolein dimer and effect consolidation of the sand particles in contactwith the dimer. After a setting time to permit curing the polymerproduction of petroleum from the formation can be initiated or renewed.

Rates of injection of the preflush solution or solutions and thetreating solution may vary from about 1 to about 3 gallons per minuteper perforation. An injection rate of from about 1.5 to 2.5 gallons perminute per perforation is desirable for consistently good results. Theinert flushing gas is employed in an amount of from about 5 to 30 cubicfeet and preferably from about to 25 cubic feet per perforation.

The flow rate of the gas mixture of the gaseous catalyst and the inertcarrier gas may vary from about 0.05 to about cubic feet per minute pergallon of dimer solution per perforation, preferably about 1-10 cubicfeet per minute per gallon of dimer solution. The concentration of thegas catalyst in the carrier gas may vary from abou 10 to about 50% byvolume, a preferred range is from about to by volume.

In the method of the present invention, it has been found that thepermeability of the consolidated sand varies wih the volume of gas usedas the pusher gas and that the compressive strength of the consolidationis in inverse proportion to the volume of the pusher gas.

Following is a description by way of example of the method of thepresent invention. In the examples the test procedure used is describedbelow.

TEST PROCEDURE A The method of the present invention was evaluated in atest chamber shaped in the form of a truncated cone measuring about 22inches in height and 18 to 20 inches in diameter, formed from a sectionof steel pipe. The chamber had an internal volume of about 3.1 cubicfeet. One end of a high pressure hose is connnected to a removable steelfitting extending about 5 inches into the test chamber. The other endwas connected to the discharge end of a pump having an output of up to10 gallons per minute at 225 p.s.i.g. The discharge end of the testchamber is fitted with a removable cover arranged to allow easy passageof fluid therethrough while retaining the sand particles therein. Theintake side of the pump was connected to various supply vessels by oneinch diameter steel pipe equipped with associated feeder pipes andvalves.

The procedure used in the evaluation was as follows:

(1) The test chamber was hand packed with the test sand and the coverput in place.

(2) Sand laden water was pumped through the cell to further pack thechamber and compact the sand. Pumping was continued until a pressurebuild-up of 20-40 p.s.i. was indicated at the pump with a throughput of5-10 gallons of water per minute.

(3) The test chamber was heated to the selected test temperature bycirculating heated water therethrough.

(4) Hot diesel oil was then passed through the cham her to remove excesswater and to simulate a water-wet oil saturated formation sand. Analcohol or acetone flush is then used to remove traces of water and oilfrom the sand.

(5) The test solution was passed into the chamber at a rate of about 2gallons per minute until all of the test solution was introduced intothe chamber.

(6) There was introduced into the test chamber the gaseous catalyst toeffect polymerization of the dimer.

(7) The treated said was permitted to set for 0.5-72 hours. The treatedsand was then removed from the chamber, split longitudinally, and corestaken therefrom for strength and water permeability measurements.

EXAMPLE 1 The test chamber was packed with a fine white sand having apermeability of about 13 darcies obtained from the Pennsylvania GlassSand Co. and designated as Oklahoma No. 1 sand. The chamber was thenheated to about 140 F. and flushed with approximately 30 gallons of acommercial diesel oil heated to 140 F. Thereafter the chamber was firstflushed with approximately 4 gallons of acetone, then treated with thetreating composition composed of 2 gallons of acrolein dimer and 2gallons of acetone. 100 ml. (0.66% by volume) of the bonding agent gammaglycidoxypropyltrimethoxysilane was also present. The chamber was thentreated with gaseous nitrogen at 50 p.s.i.g. until very little furtherfluid was evolved. Next the chamber was treated with hydrogen chlorideat 25 p.s.i.g. until the emission of hydrogen chloride was detected fromthe lower end of the chamber. The test chamber temperature increased toabout 150 F. during this treatment. After a standing time of 30 minutes,the chamber was flushed with water at 150 p.s.i.g. and a rate of 10gallons per minute. Thereafter the consolidated sand was removed andsamples were taken therefrom to determine water permeability andcompressive strengths of the samples.

One sample (1d) one inch down from the end of the injection tube and inline therewith had a permeability of 10.2 darcies and 1130 p.s.i.compressive strength. A sample (4d) four inches down from the end of theinjection tube had 11.1 darcies permeability and 1370 p.s.i. compressivestrength. Another sample (12d) one foot down from the end of the tubehad 11.7 darcies permeability and 1200 p.s.i. compressive strength. Asample (16d) 16 inches down had 9.62 darcies permeability and 1095p.s.i. compressive strength.

EXAMPLE 2 In another test a 80% by volume acrolein dimer in benzene wasused as the treating solution. Examination of the resulting consolidatedsand showed that the water permeability was about 82% of the originalsand permeability.

EXAMPLE 3 A one inch internal diameter by six inch long glass tube waspacked with a Berkley fine sand having a permeability of about 3.5darcies. The length of the packed sand was about 5 inches. Each end ofthe tube was fitted with a stopper containing a conduit passingtherethrough to permit introduction of gases and fluid therein at oneend and withdrawal of same from the other end.

In one tube the sand was packed by pressurized water and preflushed withacetone. Then 10 ml. of a solution of by volume acrolein dimer inacetone also containing 2% by volume of the silane bonding agent ofExample 1 was injected into the sand and followed by nitrogen gastreatment. Next, 33% by volume of hydrogen chloride in nitrogen waspassed into the treated sand to polymerize the dimer.

After setting the water permeability retention of the consolidated sandwas found to be 97.4% of the original permeability.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof and therefore only such limitations should be imposed asare indicated in the appendedclaims.

I claim:

1. A sand consolidating mixture consisting essentially of (a)unconsolidated sand in a petroleum-bearing formation and (b) a treatingcomposition consisting essentially of from about 25 to about 80% byvolume of acrolein dimer, from about 0.01 to about 3.0% by volume of thetreating composition of gamma-glycidoxypropyltrimethoxysilane bondingagent, and the balance a solvent for said dimer, said solvent beingselected from the group consisting of an oxygenated aliphatichydrocarbon solvent, an aromatic hydrocarbon solvent, a kerosenefraction, a diesel oil fraction, a naphthalene petroleum fraction from atopped catalytic reformate bottoms out having an Initial Boiling Pointof about 370 F. and an End Point of about 750 F., and mixtures thereof.

2. A mixture as claimed in claim 1 wherein the concentration of acroleindimer in said treating composition is from about 40 to about by volume.

3. A mixture as claimed in claim 1 wherein the concentration of theacrolein dimer in said treating composition is about 50% by volume.

4. A mixture as claimed in claim 1 wherein the concentration of thebonding agent in the treating composition is from about 0.5 to about2.0%.

5. A mixture as claimed in claim 1 wherein said solvent is acetone.

6. A mixture as claimed in claim 1 wherein said solvent is benzene.

7. A mixture as claimed in claim 1 wherein the volume ratio of treatingcomposition to said sand is in the range of from about 0.1 to about 0.2.

8. A mixture as claimed in claim 7 wherein the volume ratio is fromabout 0.12 to about 0.17.

References Cited UNITED STATES PATENTS 3,272,777 9/1966 Ishida 260-67 U3,277,058 10/1966 Bastian 260-67 U 3,408,330 10/1968 Barabas et a1.26032.8 X

OTHER REFERENCES Dow Corning: Silane Coupling Agents; 1967; pp. 1-7;copy in Group 145.

LEWIS T. JACOBS, Primary Examiner U.S. Cl. X.R. 26033.6 UA, 41 A

